<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        .wrap {
            width: 500px;
            margin: 100px auto 0;
        }

        table {
            border-collapse: collapse;
            border-spacing: 0;
            border: 1px solid #c0c0c0;
            width: 500px;
        }

        th,
        td {
            border: 1px solid #d0d0d0;
            color: #404060;
            padding: 10px;
        }

        th {
            background-color: #09c;
            font: bold 16px "微软雅黑";
            color: #fff;
        }

        td {
            font: 14px "微软雅黑";
        }

        /*tbody tr {
            background-color: #f0f0f0;
        }

        tbody tr:nth-child(odd) {
            background-color: #c0c0c0;
        }

        tbody tr:nth-child(even) {
            background-color: #d0d0d0;
        }

        tbody tr:hover {
            cursor: pointer;
            background-color: #f0f0f0;
        }*/

    </style>
</head>
<body>
<div class="wrap">
    <table>
        <thead>
        <tr>
            <th>序号</th>
            <th>姓名</th>
            <th>课程</th>
            <th>成绩</th>
        </tr>
        </thead>
        <tbody id="j_tb">
        <tr>
            <td>
                1
            </td>
            <td>柳岩</td>
            <td>语文</td>
            <td>100</td>

        </tr>
        <tr>
            <td>
                2
            </td>
            <td>苍老师</td>
            <td>日语</td>
            <td>100</td>
        </tr>
        <tr>
            <td>
                3
            </td>
            <td>凤姐</td>
            <td>营销学</td>
            <td>100</td>
        </tr>
        <tr>
            <td>
                4
            </td>
            <td>张飞</td>
            <td>数学</td>
            <td>10</td>
        </tr>
        <tr>
            <td>
                5
            </td>
            <td>小沈阳</td>
            <td>英语</td>
            <td>100</td>
        </tr>
        <tr>
            <td>
                6
            </td>
            <td>马户</td>
            <td>体育</td>
            <td>100</td>
        </tr>
        </tbody>
    </table>
</div>
<script>
    var j_tb = document.getElementById("j_tb");
    var trs = j_tb.children;
    for (var i = 0; i < trs.length; i++) {
        //trs[i].style.backgroundColor = "red";
        if (i % 2 === 0) {//索引是偶数 在页面上是奇数行
            trs[i].style.backgroundColor = "#c0c0c0";
        } else {
            trs[i].style.backgroundColor = "#d0d0d0";
        }
    }
</script>
</body>
</html>